The invention relates to a bridge bottom inspection apparatus with an operating chassis standing on the bridge and movable along the edge of the bridge and with a raisable and lowerable lift tower retained and supported by the latter which extends downwards past the edge of the bridge and to the lower end of which a work platform cantilevered beneath the bridge is attached. Such apparatuses are used instead of scaffolds or vertical lifts for the inspection or cleaning, particularly of concrete bridges, in order to reach the underside of the bridge.
Known bridge bottom inspection apparatuses, according to German Offenlegungsschrift No. 3,305,384, for example, have a box-like annular construction surrounding the lift tower, which projects from the operating chassis over the edge of the bridge and retains the lift tower and guides it in its ascending and descending movement. It is accordingly necessary for the lift tower to be of particularly flexurally rigid construction along its total length, and therefore heavy. The lifting drive unit, generally a hydraulic cylinder, is arranged in the lift tower. However, since it is necessary, for considerations of stability, for those parts of the operating chassis located on the bridge to correspond as counter weight to the parts located outside the bridge, this known construction is comparatively heavy.
Many bridges of motorways which lead through residential areas have sound insulation walls up to 3.5 m in height above or in place of the guard rail. The use of the known bridge bottom inspection apparatuses necessitates the dismantling of these sound insulation walls.
In the case of other bridges, the use of known bridge bottom inspection devices is obstructed by the fact that masts, for highway lighting or for the overhead electric lines of trolleybuses or railways, for example, are installed at comparatively short intervals along the edge of the bridge. It is necessary for the work platform and the lift tower to be retracted onto the bridge surface in front of each such obstacle to permit the operating chassis to be transported past the mast.